In a two component development system, the ability to apply sufficient developer (toner+carrier) to develop a latent image on a photoconductor enables the creation of images with high fidelity and quality. In general practice, developer “Flow” is the common metric used to describe the amount of developer delivered to a toning zone per unit time. This is accomplished by lowering a gate into a developer stream, (2″ wide) and collecting developer for a specified amount of time (0.5 Sec). This developer is then weighed and reported in units of gm/in/s. This has been correlated against certain imaging properties of the developer, such as toning contrast, background, etc.
Since the measurement of developer flow aggregates the effects of developer mass density and developer velocity, the developer flow measurement is also proportional to the product of independently measured developer bulk mass density and developer velocity. In a typical embodiment of a development station, developer is fed to a developer roller by way of a feed roller (Raw Flow) (RF). A mechanical doctor blade or metering skive is used to reduce flow variations in the developer flow along the length of the development roller to provide for metered flow (MF) on the surface of the developer roller.
The developer is a compressible powder, and control of the densification of the developer in the process of metering is beneficial for proper imaging. Excessive compression by a metering skive or doctor blade will cause the bulk density of the developer to approach its true density, causing failure as the developer forms ‘sheets’ when it reaches its maximum density and exits the development station, since developer cohesiveness increases with increasing bulk density. Therefore, control of the developer compression through the metering process is desirable.